Australia's march towards long-awaited Commonwealth Games netball gold continues - the only question now is who wears the bibs at the business end.

A nail-biting win over England aside it was been predictably plain sailing for the world champion Diamonds in the preliminary round, coasting to straightforward wins over Wales, Barbados, Trinidad and Tobago and on Wednesday a 24-goal victory over South Africa.

They now head into the final four - either defending champion New Zealand or Jamaica are in their immediate path - with the major concern confronting coach Lisa Alexander what make-up the team should take in Saturday's semi-final, and if they get through that, the gold medal playoff on Sunday.

Defending South Africa's Anna Bootha. Photo: Getty Images

Australia haven't started any of their five games with the same seven and after the 64-40 defeat of South Africa the coach said she would tailor her team specifically for their semi-final opponent, Jamaica.

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The winner faces a playoff for the gold medal with New Zealand or England.

"It's really important everyone understands we've got a really strong 12 and I don't just say that lightly," Alexander said. "They prepare as if they're playing and they find out at the team meeting, which is about two hours' before the game.

"We're going to have to play different tactics against both teams (New Zealand and Jamaica). It's horses for courses, it's which player is going to match up best and implement the game plan we need."

Alexander made three changes at half-time against South Africa, bringing on Kimberley Ravaillion for Kim Green at centre, vice-captain Bianca Chatfield for Julie Corletto at goal defence and Renae Hallinan for Sharni Layton at wing defence, before introducing replacement shooter Caitlin Thwaites and rookie goal attack Tegan Caldwell in the final quarter when the result was well and truly in the bag.

Nat Medhurst, the experienced goal attack given a spell in the final quarter alongside shooter Caitlin Bassett, said players had to prepare as if they would be starting despite not knowing until shortly before the matches. Caldwell had a been a surprise starter in the GA for the crunch group game against England but Medhurst has re-assumed the inside running to get the nod from Alexander.

"Hopefully we're making her life difficult," Medhurst said. "I think every combination that we've been able to throw out there has done a fantastic job. I know they have their selections the night before a game so they don't know generally until the 11th hour.

"Whatever combination they go with, particularly heading into finals, every player has got to be prepared, know they've done the work. At the end of the day we've all got confidence in each other."

Alexander was pleased the Diamonds had progressively improved over their five preliminary games. Captain Laura Geitz was outstanding before being subbed off in the final quarter, making five interceptions and four deflections. Layton, ordinarily an impact player, started at wing defence and ended up at goalkeeper when Geitz was given a deserved breather.

"I put that challenge to the group including the support staff f to get better and better each game and I think we've done that so I'm very pleased," Alexander said.